‘Geoffrey Cox nailed his colours firmly to the Brexit mast in his barnstorming warm-up before Theresa May’s address to the Conservative conference.’
Photograph: Wiktor Szymanowicz/Barcroft Images

When Geoffrey Cox joined the cabinet earlier this year to take on the role of attorney general, it was already perfectly clear where he stood on the biggest legal matter facing the government.

In case anyone was in any doubt, Cox nailed his colours firmly to the Brexit mast in his barnstorming warm-up speech before Theresa May’s address to the Conservative party conference last month.

He took the job, he told the Tory faithful, to help deliver on the referendum vote in 2016: “Because it will take a dogged, determined, single-minded clarity and firmness of purpose to translate that decision into reality.”

Knowing where Cox stands personally is one thing. But as attorney general he has a constitutional role to play. And a rather conflicted one at that. The attorney general is a Conservative MP and a member of a Conservative government who is expected to give independent legal advice to that government. And now he is expected to give legal advice on one of the most politically vexed questions of the time.

Brexit: Hunt says he is 'confident' UK and EU will reach deal within three weeks - Politics live

Read more

But what exactly is he supposed to be advising on? The compatibility of any deal on the Irish border with article 50? Whether a review mechanism can be unilateral? Whether the European court of justice should have any role to play on any aspect of the Irish border issue? And what happens if there is no deal on the future relationship by the end of transition in December 2020? And can the UK walk away from a legally binding divorce agreement?

And it’s also not clear whether Cox is quite the man you need in this case: his practice prior to taking up the post of attorney general was wide-ranging (and very successful). It included commercial law, human rights law and constitutional law – but not much on EU law.

But paradoxically, everyone’s an expert on the EU now that the UK is leaving. So Cox will not be alone. And the fact is no one knows for sure the answers to any of these questions because no state has triggered article 50 before, and no new customs union has been created on the hoof for a country wishing to distance itself from its closest neighbours. So it is unlikely that his legal advice will be wrong, but it may well be hedged in with caveats and uncertainties. Which is why it may be useful to all sides. Which is why all sides are pressing to see it.

This is not the first time an attorney general has been asked to give advice in a politically charged situation. Lord Goldsmith was in the hot seat when asked to give advice on the legality of military action in Iraq. If Cox is in need of bedtime reading, he could do worse than study the Chilcot inquiry’s report. That might take a while, as the inquiry devoted a whole chapter to the episode. As we know from the scale of the inquiry report, even one chapter is a lengthy piece of work. But for a quick summary of the whole legal process, try “far from satisfactory” as a quote.

Goldsmith was clear in later evidence to a parliamentary committee that the dual role of minister and legal adviser has advantages, suggesting that advice provided by an attorney who is also a member of the government “tends to be more heeded by ministers because it comes from one of their colleagues”.

From another perspective, though, might pressure to provide advice in a certain direction be all the harder to resist for a law officer who also sits around the cabinet table with the prime minister?

David Davis: don't fear no-deal Brexit despite inevitable 'hiccups'

Read more

Then there is a question always fundamental for a barrister: who is the client? When the prime minister asks for a legal opinion, is she asking for herself? Or under the convention of collective responsibility, should the advice properly be for the cabinet as a whole? Michael Gove, not a lawyer but a former justice secretary, clearly believes the latter to be the case.

And should that advice be published? Surely the cabinet should benefit from confidential legal advice, to inform its decision-making, safe in the knowledge that it will not become public knowledge? However, leaving the EU is the most important issue facing the country since the second world war. There is a strong public interest to know what advice the prime minister is receiving and for that advice to be subject to scrutiny. And there’s a good chance the advice will be leaked anyway. So all the more reason for the government to manage its publication.